An elevator system is an electromechanical assembly of equipment that contains many movable and rotating parts, which are subjected to wear and failures during the operation of the elevator system. Also, the actuators controlling the movable and rotating parts as well as the electric components and sensors connected to the said actuators are subjected to wear and failures in long-time operation of the elevator system. A failure may also be caused by unexpected external factors, such as e.g. a violent impact against the elevator door or as a result of vandalism perpetrated on the elevator. However, it is of primary importance for the operation of elevator systems that the elevator system should work correctly and above all safely in all operational conditions. Therefore, elevator systems are serviced regularly to guarantee safe operation and sufficient riding comfort. If the elevator is not serviced in time, the elevator may fail so that either passengers can not use the elevator at all or the quality of operation of the elevator deteriorates significantly. Before an actual failure, the elevator may become noisy, there may appear unpleasant vibrations of the elevator car, the stopping accuracy of the elevator car at landings may deteriorate or some other corresponding feature of the operation of the elevator may be impaired, indicating a future failure in advance. The scheduling of maintenance of elevators has traditionally been implemented either via regular maintenance according to a fixed calendar-based schedule and/or on the basis of the intensity of operation (operating history) of the elevator. The intensity of operation again depends on the place of installation of the elevator, causing individual needs regarding maintenance arrangements. If a need for maintenance is not detected until one of the actuators controlling the operation of the elevator suddenly fails and prevents preparation of the elevator, this may result in a service advice made by the client, causing extra expenses to the party responsible for the operation of the elevator. One method of eliminating or at least reducing the number of unscheduled maintenance visits is to provide the elevator with a condition monitoring system. The function of a condition monitoring system is to observe the operation of the elevator and to generate parameters representing its operational condition, on the basis of which it is possible to estimate the current operational condition of the elevator and to predict its future operational condition to enable mapping of the need for preventive maintenance. The condition monitoring system generally connects to signals indicative of the operation of the elevator, on the basis of which the system calculates parameters descriptive of the operational condition of the elevator. A sufficiently large deviation or trend of change of a parameter in relation to defined reference values produces a particular alarm about an acute or anticipated failure. The alarm information is often transmitted from the condition monitoring system to a maintenance center responsible for the maintenance of the elevator system, where the decisions regarding the required maintenance operations and their scheduling are made. For example, the systems disclosed in U.S. Pat. No. 4,512,442 Moore et al. keep count of how many times the doors have been opened and closed and send the count to a maintenance center for maintenance scheduling. Scheduling based on intensity of operation can be made more accurate by taking the type of the building into account. Certain more advanced prior-art systems additionally use operating history data of elevators for condition monitoring.
Prior-art condition monitoring systems have considerable drawbacks and deficiencies. The signals indicative of the operation of the elevator are often difficult to obtain, which is why installing and connecting the condition monitoring system to the elevator system is difficult and time-consuming. Some of the signals needed in condition monitoring may be located at a long distance from each other, for example in a control panel in the elevator machine room while some other signals are located in the elevator car. In this case it is necessary to have an extra car cable between the elevator car and the machine room to provide the wiring for the required signals to the condition monitoring system, involving a sharp increase in installation costs and time. In prior-art solutions, making a connection to the signals to be measured generally requires a galvanic connection between the condition monitoring system and the elevator control system, and often also changes in the cabling of the elevator, causing unnecessary installation work and extra costs. The galvanic connection method involves the risk of causing interference with the operation of the elevator system signals used for condition monitoring, thus producing a safety hazard. For this reason, an elevator often has to be subjected for approval by authorities supervising elevator safety to check the operation of the safety equipment after the installation of a condition monitoring system.
A further problem with prior-art solutions is that elevator systems differ significantly from each other in both electrical and functional respects. The condition monitoring system has to take into account, among other things, the current and voltage levels of the signals used in the elevator to be monitored, the timing of the signals and other elevator-specific circumstances. Condition monitoring systems implemented according to prior-art technology are therefore generally applicable only in connection with certain elevator types, but installing them in old elevators may be impossible or the required installation, modification and configuration work may become a significant cost factor.